1. Field of the Invention
The present invention relates to an ink-jet recording head driving method, an ink-jet recording apparatus provided with an ink-jet recording head to be driven by the ink-jet recording head driving method, and a computer readable medium having data stored thereon for controlling the ink-jet recording apparatus by a computer.
2. Description of the Related Art
Generally, an ink-jet recording apparatus includes a recording head having a nozzle plate provided with a plurality of jetting holes arranged in a row, a carriage mechanism for moving the recording head in a main scanning direction, i.e., a direction along the width of a recording sheet, and a sheet feed mechanism for feeding a recording sheet in a sub-scanning direction, i.e., a sheet feed direction.
The recording head has pressure generating chambers respectively communicating with the jetting holes, and pressure generating devices for varying the pressure in the pressure generating chambers. Ink pressure in the pressure generating chamber is changed by applying a driving pulse to the pressure generating device to jet an ink particle through the jetting hole.
The carriage mechanism moves the recording head along the main scanning direction. While the recording head is being moved by the carriage mechanism, the recording head jets ink particles at times specified by dot pattern data. Upon the arrival of the recording head at a terminal end of its scanning stroke, the sheet feed mechanism feeds a recording sheet in the feed direction and the carriage mechanism returns the recording head to a starting end of its stroke. After the recording sheet has been fed, the carriage mechanism moves the recording head again in the scanning direction. The recording head jets ink particles while the same is thus being moved.
The foregoing operations are repeated to record an image represented by the dot pattern data on the recording sheet.
FIG. 19A shows the waveform of a driving pulse to be applied to the pressure generating device of the recording head and FIG. 19B shows the variation of the shape of an ink surface (meniscus) in the jetting hole varying according to the driving pulse, in which time is measured on the horizontal axis and displacement is measured on the vertical axis.
As shown in FIG. 19A, the driving pulse has a filling waveform section between points P50 and P51 for expanding the pressure generating chamber to fill the pressure generating chamber with the ink, holding waveform section between points P51 and P52 for keeping the pressure generating chamber in an expanded state, and an ink jetting waveform section between points P52 and P53 for jetting the ink through the jetting hole by contracting the pressure generating chamber.
As shown in FIG. 19B, the ink in the jetting hole is drawn inward and the surface of the ink in the jetting hole becomes concave in a period corresponding to the filling waveform section between the points P50 and 51 of the driving pulse. The changing direction of the shape of the surface of the ink in the jetting hole changes from the drawing direction to the jetting direction in a period corresponding to the holding waveform section between the points P51 and P52 of the driving pulse. The ink is jetted in an ink particle in a period corresponding to the ink jetting waveform section between the points P52 and P53 of the driving pulse. This ink jetting phenomenon is ended at a point P53xe2x80x2 slightly after time corresponding to the end point P53 of the ink jetting waveform section of the driving pulse. As indicated by imaginary lines (chain lines) in FIG. 19A, driving pulses are applied successively to the pressure generating device to jet ink particles successively.
However, time intervals between the successive driving pulses which are applied to the pressure generating device should be shortened in order to achieve a recording under higher speed than that of usual. When a plurality of gradation value data are used within one printing cycle in order to record an image, the second driving pulse should be applied to the pressure generating device before the meniscus becomes fully steady after the jetting caused by the first driving pulse. As a result, the ink particle which is jetted by the second driving pulse loses its shape and is scattered.
As shown in FIG. 19B, the surface of the ink in the jetting hole vibrates at the Helmholtz vibration period TH of the pressure generating chamber when an ink particle is jetted through the jetting hole. If the starting point P54 of the succeeding driving pulse coincides with a bottom of the Helmholtz vibration, i.e., a point when the surface of the ink in the jetting hole is fully drawn inward, the ink particle is unable to hold its shape and the ink is scattered.
The present invention has been made in view of the foregoing problems and it is therefore an object of the present invention to provide an ink-jet recording head driving method capable of providing a plurality of driving pulses at optimum time intervals and of preventing the scatter of ink particles.
Another object of the present invention is to provide an ink-jet recording apparatus provided with an ink-jet recording head that is driven by the above-mentioned ink-jet recording head driving method.
Another object of the present invention is to provide a computer readable medium having a data stored thereon for controlling the above-mentioned ink-jet recording apparatus by a computer.
According to a first aspect of the present invention, an ink-jet recording head driving method of driving an ink-jet recording head having a pressure generating device corresponding to a pressure generating chamber communicating with a jetting hole and having a specific period (TH) of Helmholtz vibration, said ink-jet recording head driving method comprises: a driving pulse generating step of generating a driving pulse by taking out part of a driving signal having a time length corresponding to one printing cycle and including a plurality of driving pulse waves; and an ink jetting step of jetting an ink particle through the jetting hole by applying the driving pulse to the pressure generating device to drive the pressure generating device for a predetermined operation; wherein the driving signal has a waveform that makes a time interval between a point when a preceding ink jetting step is ended and a point when a succeeding ink jetting step is started is equal to or longer than one period (TH) of the Helmholtz vibration of a meniscus when the driving pulse generating step and the ink jetting step are repeated a plurality of times in one printing cycle to jet a plurality of the ink particles.
Preferably, the time interval is a natural multiple of the period (TH) of the Helmholtz vibration of the meniscus.
According to a second aspect of the present invention, an ink-jet recording head driving method of driving an ink-jet recording head having a pressure generating device corresponding to a pressure generating chamber communicating with a jetting hole and having a specific period (TH) of Helmholtz vibration, said ink-jet recording head driving method comprises: a driving pulse generating step of generating a driving pulse by taking out part of a driving signal having a time length corresponding to one printing cycle and including a plurality of driving pulse waves; and an ink jetting step of jetting an ink particle through the jetting hole by applying the driving pulse to the pressure generating device to drive the pressure generating device for a predetermined operation; wherein the driving signal has a waveform that makes a succeeding ink jetting step start after a point of time when a meniscus of ink in the jetting hole is drawn toward the pressure generating chamber to the utmost by the preceding ink jetting step when the driving pulse generating step and the ink jetting step are repeated a plurality of times in one printing cycle to jet a plurality of the ink particles.
According to a third aspect of the present invention, an ink-jet recording head driving method of driving an ink-jet recording head having a pressure generating device corresponding to a pressure generating chamber communicating with a jetting hole and having a specific period (TH) of Helmholtz vibration, said ink-jet recording head driving method comprises: a driving pulse generating step of generating a driving pulse by taking out part of a driving signal having a time length corresponding to one printing cycle and including a plurality of driving pulse waves; and an ink jetting step of jetting an ink particle through the jetting hole by applying the driving pulse to the pressure generating device to drive the pressure generating device for a predetermined operation; wherein the driving signal has a waveform that makes a succeeding ink jetting step start after a time point when a vibration of a meniscus of the ink in the jetting hole caused by a preceding ink jetting step is substantially stabilized when the driving pulse generating step and the ink jetting step are repeated a plurality of times in one printing cycle to jet a plurality of the ink particles.
Preferably, the point of time when the vibration of the meniscus of the ink in the jetting hole is substantially stabilized is a point of time when an amplitude of the vibration of the meniscus is decreased to about 30% of a maximum amplitude or below.
Preferably, the point of time when the vibration of the meniscus of the ink in the jetting hole is substantially stabilized is a point of time when the amplitude of the meniscus is decreased to about 15% of the maximum amplitude or below.
Preferably, the driving pulse has a filling waveform section for expanding the pressure generating chamber to fill the pressure generating chamber with the ink and an ink jetting waveform section for jetting the ink through the jetting hole by contracting the pressure generating chamber.
Preferably, the driving pulse further comprises a holding waveform section for keeping the pressure generating chamber in an expanded state caused by the filling waveform section.
Preferably, the filling waveform section is a waveform section which increases a voltage at a fixed slope so as to make the pressure generating chamber expand, and the ink jetting waveform section is a waveform section which decreases a voltage at a fixed slope so as to make the pressure generating chamber contract.
Preferably, the driving pulse has an ink jetting waveform section that makes the pressure generating chamber held in an expanded state contract to jet an ink particle through the jetting hole.
According to a fourth aspect of the present invention, an ink-jet recording apparatus comprises: an ink-jet recording head provided with a pressure generating chamber communicating with a jetting hole through which an ink particle is jetted and having a specific period (TH) of Helmholtz vibration, and a pressure generating device corresponding to the pressure generating chamber; and a head driving unit that generates a driving pulse by tanking out part of a driving signal having a time length corresponding to one printing cycle and including a plurality of driving pulse waves and applies the driving pulse to the pressure generating device to drive the pressure generating device for a predetermined operation to jet an ink particle through the jetting hole; wherein the driving signal has a waveform that makes a time interval between a point when a preceding ink jetting step is ended and a point when a succeeding ink jetting step is started is equal to or longer than one period (TH) of the Helmholtz vibration of a meniscus when the head driving unit repeats the ink jetting step a plurality of times in one printing cycle to jet a plurality of the ink particles.
Preferably, the time interval is a natural multiple of the period (TH) of the Helmholtz vibration of the meniscus.
According to a fifth aspect of the present invention, an ink-jet recording apparatus comprises: an ink-jet recording head provided with a pressure generating chamber communicating with a jetting hole through which an ink particle is jetted and having a specific period (TH) of Helmholtz vibration, and a pressure generating device corresponding to the pressure generating chamber; and a head driving unit that generates a driving pulse by tanking out part of a driving signal having a time length corresponding to one printing cycle and including a plurality of driving pulse waves and applies the driving pulse to the pressure generating device to drive the pressure generating device for a predetermined operation to jet the ink particle through the jetting hole; wherein the driving signal has a waveform that makes a succeeding ink jetting step start after a point of time when a meniscus of the ink in the jetting hole is drawn toward the pressure generating chamber to the utmost by a preceding ink jetting step when the head driving unit repeats the ink jetting step a plurality of times in one printing cycle to jet a plurality of the ink particles.
According to a sixth aspect of the present invention, an ink-jet recording apparatus comprises: an ink-jet recording head provided with a pressure generating chamber communicating with a jetting hole through which an ink particle is jetted and having a specific period (TH) of Helmholtz vibration, and a pressure generating device corresponding to the pressure generating chamber; and a head driving unit that generates a driving pulse by tanking out part of a driving signal having a time length corresponding to one printing cycle and including a plurality of driving pulse waves and applies the driving pulse to the pressure generating device to drive the pressure generating device for a predetermined operation to jet the ink particle through the jetting hole; wherein the driving signal has a waveform that makes a succeeding ink jetting step start after a time point when a vibration of a meniscus of the ink in the jetting hole caused by a preceding ink jetting step is substantially stabilized when the ink jetting step performed by the head driving unit is repeated a plurality of times in one printing cycle to jet a plurality of the ink particles.
Preferably, the point of time when the vibration of the meniscus of the ink in the jetting hole is substantially stabilized is a point of time when an amplitude of the vibration of the meniscus is decreased to about 30% of a maximum amplitude or below.
Preferably, the point of time when the vibration of the meniscus of the ink in the jetting hole is substantially stabilized is a point of time when the amplitude of the meniscus is decreased to about 15% of the maximum amplitude or below.
Preferably, the driving pulse has a filling waveform section for expanding the pressure generating chamber to fill the pressure generating chamber with the ink and an ink jetting waveform section for jetting the ink through the jetting hole by contracting the pressure generating chamber.
Preferably, the driving pulse further comprises a holding waveform section for keeping the pressure generating chamber in an expanded state caused by the filling waveform section.
Preferably, the filling waveform section is a waveform section which increases a voltage at a fixed slope so as to make the pressure generating chamber expand, and the ink jetting waveform section is a waveform section which decreases a voltage at a fixed slope so as to make the pressure generating chamber contract.
Preferably, the driving pulse has an ink jetting waveform section that makes the pressure generating chamber held in an expanded state contract to jet the ink particle through the jetting hole.
According to a seventh aspect of the present invention, a computer readable medium has a data on a driving signal waveform stored thereon which is read by a computer to control a jetting of an ink particle by an ink-jet recording apparatus, the ink-jet recording apparatus comprising an ink-jet recording head provided with a pressure generating chamber communicating with a jetting hole through which an ink particle is jetted and having a specific period (TH) of Helmholtz vibration, and a pressure generating device corresponding to the pressure generating chamber; and a head driving unit that generates a driving pulse by tanking out part of a driving signal having a time length corresponding to one printing cycle and including a plurality of driving pulse waves and applies the driving pulse to the pressure generating device to drive the pressure generating device for a predetermined operation to jet the ink particle through the jetting hole; wherein the driving signal which is produced using the data has a waveform that makes a time interval between a point when a preceding ink jetting step is ended and a point when a succeeding ink jetting step is started is equal to or longer than one period (TH) of the Helmholtz vibration of a meniscus when the head driving unit repeats the ink jetting step a plurality of times in one printing cycle to jet a plurality of the ink particles.
Preferably, the time interval is a natural multiple of the period (TH) of the Helmholtz vibration of the meniscus.
According to an eighth aspect of the present invention, a computer readable medium has a data on a driving signal waveform stored thereon which is read by a computer to control a jetting of an ink particle by an ink-jet recording apparatus, the ink-jet recording apparatus comprising an ink-jet recording head provided with a pressure generating chamber communicating with a jetting hole through which an ink particle is jetted and having a specific period (TH) of Helmholtz vibration, and a pressure generating device corresponding to the pressure generating chamber; and a head driving unit that generates a driving pulse by tanking out part of a driving signal having a time length corresponding to one printing cycle and including a plurality of driving pulse waves and applies the driving pulse to the pressure generating device to drive the pressure generating device for a predetermined operation to jet the ink particle through the jetting hole; wherein the driving signal which is produced using the data has a waveform that makes a succeeding ink jetting step start after a point of time when a meniscus of the ink in the jetting hole is drawn toward the pressure generating chamber to the utmost by a preceding ink jetting step when the head driving unit repeats the ink jetting step a plurality of times in one printing cycle to jet a plurality of the ink particles.
According to a ninth aspect of the present invention, a computer readable medium has a data on a driving signal waveform stored thereon which is read by a computer to control a jetting of an ink particle by an ink-jet recording apparatus, the ink-jet recording apparatus comprising an ink-jet recording head provided with a pressure generating chamber communicating with a jetting hole through which an ink particle is jetted and having a specific period (TH) of Helmholtz vibration, and a pressure generating device corresponding to the pressure generating chamber; and a head driving unit that generates a driving pulse by tanking out part of a driving signal having a time length corresponding to one printing cycle and including a plurality of driving pulse waves and applies the driving pulse to the pressure generating device to drive the pressure generating device for a predetermined operation to jet the ink particle through the jetting hole; wherein the driving signal which is produced using the data has a waveform that makes a succeeding ink jetting step start after a time point when a vibration of a meniscus of the ink in the jetting hole caused by a preceding ink jetting step is substantially stabilized when the ink jetting step performed by the head driving unit is repeated a plurality of times in one printing cycle to jet a plurality of the ink particles.
Preferably, the point of time when the vibration of the meniscus of the ink in the jetting hole is substantially stabilized is a point of time when an amplitude of the vibration of the meniscus is decreased to about 30% of a maximum amplitude or below.
Preferably, the point of time when the vibration of the meniscus of the ink in the jetting hole is substantially stabilized is a point of time when the amplitude of the vibration of the meniscus is decreased to about 15% of the maximum amplitude or below.
Preferably, the driving pulse has a filling waveform section for expanding the pressure generating chamber to fill the pressure generating chamber with the ink and an ink jetting waveform section for jetting the ink through the jetting hole by contracting the pressure generating chamber.
Preferably, the driving pulse further comprises a holding waveform section for keeping the pressure generating chamber in an expanded state caused by the filling waveform section.
Preferably, the filling waveform section is a waveform section which increases a voltage at a fixed slope so as to make the pressure generating chamber expand, and the ink jetting waveform section is a waveform section which decreases a voltage at a fixed slope so as to make the pressure generating chamber contract.
Preferably, the driving pulse has an ink jetting waveform section that makes the pressure generating chamber held in an expanded state contract to jet the ink particle through the jetting hole.